The present invention concerns a detector for monitoring rotation including functions for learning the passage frequency to be monitored, for selecting an operating range, and for calculating a triggering frequency. This detector may be used, for example, for monitoring the speed of rotary movement.
Detectors for monitoring rotation are frequently used in a great number of industries in order to monitor movement, sliding, breakage of a conveyor belt, and the like. Rotation detectors are capable of combining information acquisition functions of a conventional detector by means of a sensor unit and simple processing functions by counting information received by the detector during a given time and by comparing the information received with a triggering frequency preset on the apparatus. A binary signal resulting from this comparison is provided at the output. An economical apparatus is thus obtained, well suited for processing simple subspeed or overspeed problems. However, the operator must adjust the triggering and/or resetting frequency of the device according to the desired application. The adjustment is generally made by using the screw of a potentiometer mounted on the rotation detector. The adjustment is tedious because the operator does not have any feedback information on the adjustment which he has just carried out.
Document FR 2621119 describes a device for signalling the exceeding of a speed limit. This device includes input means actuated by an operator for storing a reference threshold with which a measured speed will be compared. Document EP 0843177 also describes a device for measuring the speed of a locomotion means, where an operator may select one or more reference thresholds. However, in addition to the fact that these devices are only provided for monitoring overspeed and not for monitoring subspeed, they do not allow an operator to be able to select different operating ranges about a same reference value.
The object of the invention is to provide an operator with a simplification of the adjustment of the detector, and to provide him with greater flexibility in its use by enabling rapid alteration of the accuracy of the device, while maintaining the most economical solution as possible for such a detector.
For this purpose, the invention describes a detector for monitoring rotation, in front of which a target passes. In order to monitor a relative passage frequency, the detector includes a sensor unit sensitive to the passage of the target, connected through a detection stage to the input of a microcontroller that delivers a binary output signal by means of a power stage. The detector includes means for conversing with the operator, connected to the microcontroller in order to set the detector in a working mode or in a learning mode. The learning mode enables the microcontroller to measure the normal passage frequency and to select an operating range for the detector.
The operating range is selected by an operator from a plurality of predefined ranges within the microcontroller through the conversational means. The microcontroller calculates, for the normal calculated passage frequency and from the selected operating range, a triggering frequency different from the normal passage frequency. It also calculates a resetting frequency between the triggering frequency and the normal passage frequency. For use in subspeed monitoring, the triggering frequency is lower than the normal passage frequency. For overspeed monitoring, the triggering frequency is greater than the normal passage frequency.